1. Field of the Invention
The present invention relates to a power transmission system of a hybrid vehicle. More particularly, the present invention relates to a power transmission system of a hybrid vehicle which can implement a fixed-stage gear in EV mode traveling and high-speed traveling by an electronic continuous variable transmission (E-CVT) and two motor/generators.
2. Description of Related Art
The environmentally-friendly technology for vehicles is a critical technology determining the fate of the future vehicle industry and the advanced automobile manufacturers have devoted all their strength to develop environmentally-friendly vehicles for satisfying the rules of environment and fuel efficiency.
Accordingly, the automobile manufacturers have developed an electric vehicle (EV), a hybrid electric vehicle (HEV), and a fuel cell electric vehicle (FCEV) for the future vehicle technology.
There are various technical limitations such as weight and cost in the future vehicles, such that the automobile manufacturers are interested in hybrid vehicles as an alternative plan of practical problems for satisfying regulations of exhaust gas and improving fuel efficiency, and are in keen competition with each other to put the vehicles to practical use.
Hybrid vehicles are vehicles using two or more energy sources (power sources) and may be implemented in various types, in which, generally, a gasoline engine or a diesel engine which generally uses fossil fuel as the power source in the related art and a motor/generator driven by electric energy are combined.
The hybrid vehicles use a motor/generator with relatively high low-speed torque characteristics as a main power source at a low speed and use an engine with relatively high high-speed torque characteristics as the main power source at a high speed.
Accordingly, the hybrid vehicles stops the engine using fossil fuel and uses the motor generator in a low speed range, such that they are advantageous in improving fuel efficiency and reducing exhaust gas.
The power transmission systems of the hybrid vehicles are different in durability, power transmission efficiency, and size in accordance with the connecting configurations, such that studies for achieving a compact power transmission system that is strong with a loss of power have been conducted.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.